PROJECT SUMMARY The long-term goal of the current proposal is to generate a new class of small molecules to treat familial hypercholesterolemia. Familial hypercholesterolemia (FH) patients suffer from excessively high levels of Low Density Lipoprotein Cholesterol (LDL-C), which if left untreated results in death from severe cardiovascular disease. FH is caused primarily by mutations in the LDL receptor (LDLR) that prevent the uptake and clearance of LDL-C by the liver. Although 4 major classes of LDL-C lowering drugs exist, (statins, bile acid sequestrants, PCSK9 inhibitors, and cholesterol absorption inhibitors), all are inefficient at treating FH patients with homozygous LDLR gene mutations (hoFH). Two new drugs, Lomitapide and Mipomersin, have recently been approved for hoFH treatment. Both act independently of the LDLR to control lipoprotein production by regulating APOB levels. Unfortunately, both drugs have serious side effects including accumulation of liver triglycerides, which result in hepatic steatosis, elevated liver enzyme levels, and liver damage. With hoFH occurring at frequency of up to 1/160K live births, there is a need for new treatments that are safe and effective. The identification of novel small molecules to treat hoFH, has been hampered by the lack of a drug discovery platform that can recapitulate the deficiencies in liver function and cholesterol metabolism that are present in FH patients. To circumvent this barrier, we generated induced pluripotent stem cells from a hoFH patient. When the hoFH iPSCs were induced to form hepatocytes, they recapitulated the pathophysiology of FH in culture. We used this platform to screen a proprietary drug library and identified a family of structurally related small molecules that could reproducibly reduce the production of Apolipoprotein B, which is the central protein component of LDL-C. Preliminary studies demonstrate that these small molecules are highly effective, do not cause abnormal lipid accumulation, have a novel mechanism of action, and a chemical structure that is unrelated to any known cholesterol lowering drug. In this phase I STTR application, we propose pre-clinical studies to test the hypothesis that our lead compounds can effectively lower LDL-cholesterol and improve symptoms in physiologically relevant in vivo models.